Copper is essential for any kind of living. It delivers electricity and clean water into our homes and cities and makes an important contribution to sustainable development. More than that, it is essential for life itself. The following describes different properties of copper, divided by type (chemical, mechanical and physical).
Chemical properties of copper
All common metals and alloys react with a moist atmosphere and corrode. Only in hot/dry (deserts) and cold/dry environments do metals resist corrosion. However, due to the chemical properties of copper, the corrosion process is very slow. The corrosion resistance of copper and copper alloys is based on their ability to form stable compounds that provide some protection from corrosive attack. When exposed to the atmosphere, protective layers of oxides and poorly soluble basic salts form on the surface of copper and copper alloys. Suitable alloying elements can positively influence the formation of these coatings.
The copper element is in the same periodic table group as silver and gold. Therefore, it is relatively inert against chemicals. In most of its compounds it can have the valency (oxidation state) of +I or the valency state +II. The aqueous solutions of copper ions in the oxidation state +II have a blue colour, whereas copper ions in the oxidation state +I are colourless. Copper and copper compounds give a greenish color to a flame.
Mechanical properties of copper
The primary mechanical properties of copper—hardness, strength and ductility—determine its condition. The material condition (alternative term: temper) is designated in standards either by the letter H, representing a minimum hardness, or the letter R, representing a minimum tensile strength.
Copper can be supplied in a range of conditions from annealed (soft) to fully hard, which is obtained by cold working.
Annealed copper (H040) has a minimum hardness of 40HV, a minimum tensile strength 200 N/mm2(R200) with fully cold worked copper (H110) having a hardness of 110HV minimum and tensile strength of 360 N/mm² ( R360) minimum.
The ductility of fully cold worked copper is much less than in the annealed condition with a value of 2% elongation.
The strength and hardness of copper can also be increased by alloying, but this results in a decrease in electrical conductivity. The strongest copper alloy of all is produced by alloying with beryllium, followed by an age hardening heat treatment resulting in a tensile strength of up to 1500 N/mm².
Physical properties of copper
The generation, transmission and use of electricity has transformed the modern world. This has been made possible by copper (of at least 99.9% purity), which has the best electrical conductivity of any common metal – one of the more well-known physical properties of copper. It is available in wrought form as wire, cable, strip and busbars and as castings for such components as electrical switchgear and welding equipment.
Copper is a good conductor of heat (about 30 times better than stainless steel and 1.5 times better than aluminium). This leads to applications where rapid heat transfer is required such as heat exchangers in air conditioning units, vehicle radiators, heat sinks in computers, heat sealing machines and televisions, and as water-cooled furnace components.
Good-quality spark plugs have a central copper electrode to enable heat to be removed and prevent overheating. The best quality saucepans are copper bottomed to ensure uniform, rapid heating.
Ease of joining
Copper can be readily joined by brazing, soldering, bolting or adhesives. In industry, this is very useful for plumbing pipework and joining busbars, which are vital elements of power distribution systems. Elsewhere, it is also an important feature for artists crafting sculptures and statues, and for jewellery makers and other artisans working with this beautiful metal.